Does the Addition of M-Mode to B-Mode Ultrasound Increase the Accuracy of Identification of Lung Sliding in Traumatic Pneumothoraces?

OBJECTIVES: It is unknown whether the addition of M-mode to B-mode ultrasound (US) has any effect on the overall accuracy of interpretation of lung sliding in the evaluation of a pneumothorax by emergency physicians. This study aimed to determine what effect, if any, this addition has on US interpretation by emergency physicians of varying training levels. METHODS: One hundred forty emergency physicians were randomized via online software to receive a quiz with B-mode clips alone or B-mode with corresponding M-mode images and asked to identify the presence or absence of lung sliding. RESULTS: The sensitivity, specificity, and accuracy of the diagnosis of lung sliding with and without M-mode US were compared. Overall, the sensitivities, specificities, and accuracies of B-mode + M-mode US versus B-mode US alone were 93.1% and 93.2% (P = .8), 96.0% and 89.8% (P < .0001), and 91.5% and 94.5% (P = .0091), respectively. A subgroup analysis showed that in those providers with fewer than 250 total US scans done previously, M-mode US increased accuracy from 88.2% (95% confidence interval, 86.2%-90.2%) to 94.4% (92.8%-96.0%; P = .001) and increased the specificity from 87.0% (84.5%-89.5%) to 97.2% (95.4%-99.0%; P < .0001) compared with B-mode US alone. There was no statistically significant difference observed in the sensitivity, specificity, and accuracy of B-mode + M-mode US compared with B-mode US alone in those with more than 250 scans. CONCLUSIONS: The addition of M-mode images to B-mode clips aids in the accurate diagnosis of lung sliding by emergency physicians. The subgroup analysis showed that the benefit of M-mode US disappears after emergency physicians have performed more than 250 US examinations.

Utility of Lung Ultrasonography for Detection of Pleural Adhesions in Dogs.

OBJECTIVES: To assess lung respiratory movement ("lung sliding") in dogs using B-mode ultrasonography (US) and to develop a method that assesses adhesions between the parietal pleura and the lung. METHODS: Seventeen male beagles were anesthetized, and respiratory management was performed with intermittent positive pressure ventilation. Lung-sliding assessments and adhesion examinations were performed with lung US under general anesthesia before and 2 weeks after thoracotomy. Lung sliding was scored on a 4-level scale based on the percentage of the area that showed lung sliding (3, an area of roughly ≥80% of the intercostal space; 2, about 50% of the area of the intercostal space; 1, a small area of the intercostal space; or 0, movement absent); scores of 0, 1, and 2 indicated adhesions, whereas a score of 3 indicated no adhesions. The animals were then euthanized, and necropsy was performed to examine pleural adhesions. RESULTS: Lung US and necropsy findings were compared. The median lung-sliding score for the 12 sites with pleural adhesions on necropsy was 1.5, whereas it was 3.0 for the 532 sites without pleural adhesions. The lung-sliding score was significantly lower in the group with adhesions (P < .0001). Adhesion sites detected on necropsy were in accordance with the sites that had decreased lung-sliding scores. Lung US could detect pleural adhesions with sensitivity of 100.0% and specificity of 87.8%. CONCLUSIONS: Examination of lung sliding by thoracic US has high diagnostic value for detecting canine pleural adhesions and is useful in predicting adhesion sites before thoracic surgery in healthy dogs.

Lung Ultrasonography in Patients With Idiopathic Pulmonary Fibrosis: Evaluation of a Simplified Protocol With High-Resolution Computed Tomographic Correlation.

OBJECTIVES: To compare a simplified ultrasonographic (US) protocol in 2 patient positions with the same-positioned comprehensive US assessments and high-resolution computed tomographic (CT) findings in patients with idiopathic pulmonary fibrosis. METHODS: Twenty-five consecutive patients with idiopathic pulmonary fibrosis were prospectively enrolled and examined in 2 sessions. During session 1, patients were examined with a US protocol including 56 lung intercostal spaces in supine/sitting (supine/sitting comprehensive protocol) and lateral decubitus (decubitus comprehensive protocol) positions. During session 2, patients were evaluated with a 16-intercostal space US protocol in sitting (sitting simplified protocol) and left/right decubitus (decubitus simplified protocol) positions. The 16 intercostal spaces were chosen according to the prevalence of idiopathic pulmonary fibrosis-related changes on high-resolution CT. The sum of B-lines counted in each intercostal space formed the US scores for all 4 US protocols: supine/sitting and decubitus comprehensive US scores and sitting and decubitus simplified US scores. High-resolution CT-related Warrick scores (J Rheumatol 1991; 18:1520-1528) were compared to US scores. The duration of each protocol was recorded. RESULTS: A significant correlation was found between all US scores and Warrick scores and between simplified and corresponding comprehensive scores (P < .0001). Decubitus simplified US scores showed a slightly higher correlation with Warrick scores compared to sitting simplified US scores. Mean durations of decubitus and sitting simplified protocols were 4.76 and 6.20 minutes, respectively (P < .005). CONCLUSIONS: Simplified 16-intercostal space protocols correlated with comprehensive protocols and high-resolution CT findings in patients with idiopathic pulmonary fibrosis. The 16-intercostal space simplified protocol in the lateral decubitus position correlated better with high-resolution CT findings and was less time-consuming compared to the sitting position.

Characterization of Thoracic Pathophysiologic Conditions in Patients Receiving High-Frequency Oscillatory Ventilation: Pediatric Experience.

High-frequency oscillatory ventilation (HFOV) is a mode of mechanical ventilation used in severe pediatric respiratory failure. Thoracic ultrasound (US) is a powerful tool for diagnosing acute pathophysiologic conditions during spontaneous respiration and conventional noninvasive and invasive mechanical ventilation. High-frequency oscillatory ventilation differs from conventional modes of ventilation in that it does not primarily use bulk flow delivery for gas exchange but, rather, a number of alternative mechanisms as the result of pressure variations oscillating around a constant distending pressure. Thoracic US has not been well described in patients receiving HFOV, and it is unclear whether the US findings for assessing thoracic pathophysiologic conditions during conventional ventilation are applicable to patients receiving HFOV. We discuss the similarities and differences of thoracic US findings in patients who are spontaneously breathing or receiving conventional ventilation compared to those in patients receiving HFOV.

Accuracy of Medical Students in Detecting Pleural Effusion Using Lung Ultrasound as an Adjunct to the Physical Examination.

OBJECTIVES: This study compared the accuracy of medical students in identifying pleural effusion in hospitalized patients using the physical examination versus lung ultrasound (US). METHODS: Fourth-year medical students (n = 14) received 20 hours of general practical US training (including 2 hours of specialized lung US training) plus theoretical and video documentation. The students used the physical examination alone versus the physical examination plus lung US to document the presence or absence of pleural effusion in the right and left hemithoraces of hospitalized patients (n = 11 patients; 22 hemithoraces examined 544 times in total). The reference standard for identification of pleural effusion was a lung US examination by 2 expert point-of-care sonographers. RESULTS: The odds of correctly identifying the presence versus absence of pleural effusion was 5 times greater with lung US as an adjunct to the physical examination compared to the physical examination alone (odds ratio [OR], 5.1 from multivariate logistic regression; 95% confidence interval, 3.3-8.0). The addition of lung US to the physical examination resulted in an increase in sensitivity from 48% to 90%, in specificity from 73% to 86%, and in accuracy from 60% to 88%. The benefits of using US were greater when pleural effusion was present versus absent (OR, 10.8 versus 2.4) and when examining older versus younger patients (OR, 10.2 versus 2.8). CONCLUSIONS: These results demonstrate that medical students' ability to detect the presence or absence of pleural effusion is superior when using lung US as an adjunct to the physical examination than when using the physical examination alone.

Lung Ultrasound Findings Detected During Inpatient Echocardiography Are Common and Associated With Short- and Long-term Mortality.

OBJECTIVES: Although pulmonary abnormalities are easily seen with standard echocardiography or pocket-sized ultrasound devices, we sought to observe the prevalence of lung ultrasound apical B-lines and pleural effusions and their associations with inpatient, 1-year, and 5-year mortality when found in hospitalized patients referred for echocardiography. METHODS: We reviewed 486 initial echocardiograms obtained from consecutive inpatients over a 3-month period, in which each examination included 4 supplemental images of the apex and the base of both lungs. Kaplan-Meier survival curves were used to compare mortality rates among patients with versus without lung findings. Cox proportional hazard regression was used to determine the relative contributions of age, sex, effusions, and B-lines to overall mortality. RESULTS: Of the 486 studies, the mean patient age ± SD was 68 ± 17 years; the median age was 70 years (interquartile range, 27 years); and 191 (39%) had abnormal lung findings. The presence versus absence of abnormal lung findings was related to initial-hospital (8.9% versus 2.0%; P = .001), 1-year (33% versus 14%; P < .001), and 5-year (56% versus 31%; P < .001) mortality. Ultrasound apical B-lines and pleural effusions were both independently associated with increased mortality during initial hospitalization (hazard ratio [HR], 4.3; 95% confidence interval [CI], 1.7-11.0; and HR, 2.5; 95% CI, 1.1-6.0, respectively). Pleural effusions were also associated with increased 1-year mortality (HR, 2.3; 95% CI, 1.5-3.4). CONCLUSIONS: In hospitalized patients undergoing echocardiography, the simple addition of 4 quick 2-dimensional pulmonary views to the echocardiogram often detects abnormal findings that have important implications for short- and long-term mortality.

Validity of Ultrasound Lung Comets for Assessment of the Severity of Interstitial Pneumonia.

OBJECTIVES: Ultrasound (US) lung comets are often observed in patients with interstitial lung disease or congestive heart failure, but few studies have explored the clinical importance of US lung comets in patients with the former condition. We explored whether the US lung comet number could be used to assess the severity of interstitial pneumonia. METHODS: Forty stable patients with interstitial pneumonia were examined. Lung comets evident on transthoracic US imaging in 12 selected regions of the posterior chest wall were analyzed. We defined lung comets accompanied by thickened and irregular pleural lines as interstitial US lung comets; these predominated in patients with interstitial pneumonia. The total number of interstitial US lung comets was correlated with the data from chest high-resolution computed tomography, pulmonary function tests, serologic tests, and the 6-minute walk test. RESULTS: The 40 patients included 16 with idiopathic pulmonary fibrosis and 24 with nonspecific interstitial pneumonia. Thirty-four patients had interstitial US lung comets, which were more common in the lower than the upper lung area. Good correlations were evident between the lung comet number and the extent of the reticular pattern on chest high-resolution computed tomography (r = 0.710; P < .01), predicted forced vital capacity (r = -0.614; P < .01), and lung diffusion capacity for carbon monoxide (r = -0.577; P < .01). Notably, the lung comet number had a strong negative correlation with the percutaneous oxygen saturation level after the 6-minute walk test (r = -0.751; P < .01). CONCLUSIONS: The number of interstitial US lung comets evident on transthoracic US imaging may be a valuable marker of disease severity in patients with interstitial pneumonia.

Does Intravenous Infusion Influence Diagnostic Ultrasound-Induced Pulmonary Capillary Hemorrhage?

OBJECTIVES: Pulmonary diagnostic ultrasound (US) can induce pulmonary capillary hemorrhage (PCH) in mammals. This singular biological effect of diagnostic US imaging was discovered more than 25 years ago but remains poorly understood. Our objective here was to investigate rapid infusion of intravenous fluids as a possible stressor for capillaries, which might enhance pulmonary diagnostic US-induced PCH. METHODS: Rats were anesthetized with Telazol (Zoetis, Inc, Kalamazoo, MI), which yielded relatively low pulmonary diagnostic US-induced PCH, or Telazol and xylazine, which yielded relatively high pulmonary diagnostic US-induced PCH. Groups of rats were not infused or infused either with normal saline, 10% mannitol, or 5% albumin. Rats were scanned in a warmed water bath with B-mode US for 5 minutes with a 7.6-MHz linear array set to different mechanical index values to obtain exposure response information. Pulmonary capillary hemorrhage was observed as comet tail artifacts in the image and measured on the lung surface. RESULTS: For Telazol anesthesia, all of the PCH results were very low, with no significant differences at the maximum output with an in situ peak rarefactional pressure amplitude of 2.1 MPa (on-screen mechanical index, 0.9). The addition of xylazine to the Telazol anesthetic significantly enhanced the PCH (P < .001) without infusion and likewise for the mannitol and albumin infusion. Saline infusion eliminated this enhancement, with significantly reduced PCH for Telazol-plus-xylazine anesthesia (P < .001); however, both mannitol and albumin infusion resulted in significantly more PCH than saline infusion (P < .01). CONCLUSIONS: These results show PCH dependence on the specific intravenous infusion fluid and illustrate the complex importance of physiologic parameters for US-induced PCH.